1. Field of the Invention
The present invention generally relates to a driving circuit for a display apparatus, and a method of driving the display apparatus.
2. Description of the Related Art
There is a display apparatus, in which a plurality of scanning electrodes and a plurality of signal electrodes are arranged in a matrix shape, and an EL (Electroluminescence) element is connected to one scanning electrode and one signal electrode at each intersection of the scanning electrode and the signal electrode. By supplying a constant current driving signal to a desired signal electrode with respect to one common scanning electrode, the corresponding EL element is set in a lighting condition.
In this type of display apparatus, the EL element is degraded in its ability after it is used for a long time, so that a voltage drop Vf in the forward direction becomes large, and that the characteristic of luminance versus electric current, is also degraded. In this manner, in a constant current driving method, as the EL element is degraded in its ability, the luminance of the EL element is also gradually degraded.
Therefore, countermeasures may be proposed to prevent the voltage drop Vf in the forward direction.
Firstly, in this type of display apparatus, the voltage to be supplied to the driving device of the display apparatus, may be set high in advance so as to deal with the expected increase of the voltage drop Vf in the forward direction of the EL element. However, if the voltage to be supplied to the driving device is set high in advance in this manner, the high voltage is supplied to the driving device even in an initial condition where the ability of the EL element is not degraded. As a result, the electric power consumed by the transistors in the driving device is increased, so that there arises a waste of energy consumption.
Secondly, the current supplied from the driving device for the display apparatus, may be set high in advance so as to deal with the expected increase of the voltage drop Vf in the forward direction of the EL element. However, if this current supplied from the driving device is set high in advance in this manner, the high current is supplied from the driving device even in an initial condition where the ability of the EL elements is not degraded. As a result, the electric power consumed by transistors in the driving device is increased, so that there arises a waste of energy consumption, too.